1. Field of the Invention
The present invention relates to a light source device including a laser light source used well for a projector, projector apparatus including the light source device and projection method.
2. Description of the Related Art
A rear projector using a laser light as a light source, which includes (a) a light source for emitting laser light toward a screen, (b) a scanning means for scanning a laser light emitted by the light source, (c) diffusing means for diffusing the laser light scanned by the scanning means and (d) focusing means for focusing the laser light diffused by the diffusing means on a screen, has been disclosed in Japanese Patent Application Publication No. 2007-025466 to reduce the speckle noise occurred on a screen.
By the way, laser diodes generally used as a light source for emitting laser light do not oscillate until the current value supplied to the laser diodes increases to the threshold current value. When the current value supplied to the laser diodes is larger than the threshold current value, the laser diodes oscillates linearly.
Therefore, higher emission efficiency is obtained when the laser diodes is driven by a bigger current value within operating limit current value of the laser diodes.
Thus, it is more efficient to drive the laser diodes intermittently by double current value and 50% duty ratio than to drive the laser diodes by a constant current value to get the same electrical output power in a unit time.
Nevertheless, as shown in the above Patent Document, it is required that the light source continues emitting in a constant output if the laser diodes are used as the light source of the projector.
Therefore it was impossible to employ the intermittent driving mentioned above, and as a result the light source had to be driven in lower emission efficiency.
The present invention has been made in view of the foregoing problems of conventional technology. It is accordingly an object of the present invention to provide a light source unit, projector apparatus, and projection method, which can drive laser diodes with higher emission efficiency and obtain a constant luminance in succession.